Method of constructing a miniature solid propellant rocket



Dec. 21, 1965 B. B. GOULD 3,224,317

METHOD OF CONSTRUCTING A MINIATURE SOLID PROPELLANT ROCKET Filed sept. 22, 1961 United States Patent 3,224,317 METHOD 0F CONSTRUCTING A MINIATURE SOLID PROPELLANI ROCKET Bert B. Gould, Berkeley, Calif., assigner, by mesne assignments, to MB Associates, San Ramon, Calif. Filed Sept. 22, 1961, Ser. No. 140,691 3 Claims. (Cl. 86-1) This invention relates to methods for construction of cases for miniature solid propellant rockets.

Cases for large rockets are constructed by conventional methods such as deep drawing, rolling and welding, or extruding, and present no unusual difiiculties. After a large case has been made the propellant grain, nozzle, guidance assembly and tins may be attached. The miniature solid propellant rockets to which this invention relates are very small, wherein the case has a diameter of of 1,5 to 3 millimeters and a length of 8 to 35 millimeters. construction of cases of such size by conventional methods is diiiicult and expensive but novel methods of construction that would be impractical in large sizes may be ideal for miniature rockets.

According to the present invention, methods of construction of rocket cases have been devised wherein the case is formed using the internal components, i .e. the propellant grain as a forming guide. The simplest such method requires only the dipping of a propellant grain and nozzle in a polymerizing liquid such as alphacyanoacrylate, the sodium salt of polyacrylic acid, catalyzed epoxy resin or catalyzed polyester resin. A resin or plastic dissolved in a solvent may of course be used also, but in such case it is preferable that a protective coating, either dipped or sprayed be first applied to avoid altering the propellant.

According to another embodiment of the invention, a spray coating of graphite or other conductive material is iirst applied to the propellant grain and a metal case is then plated onto the propellant grain. Fins may be attached to said case by metal-bonding.

For higher strength/weight ratios, iibers oriented to increase hoop strength may be added in a matrix of polymerizing plastic. G-lass or metal iiber may be wound around the propellant grain and nozzle under a spray lof catalyzed epoxy or polyester resin.

Except for the nose section, a plastic case complete with iins may be continuously extruded around a center mandrel of propellant, also continuously extruded. This co-extrusion requires only cutting to length, sharpening and raking the reading edges of the fins, and attaching a nose and nozzle to make a finished projectile ready for fuzing. A number of fabrication and assembly operations are thereby sirnpliiied or eliminated.

In the drawings forming part of this application:

FIGURE 1 is a section view through a propellant grain emerging from a dipped bath.

FIGURE 2 is a section view of a propellant grain immersed in a plating solution.

FIGURE 3 is a perspective view of a grain being wound with a iiat iiber.

FIGURE 4 is a section view through a co-extrusion die.

FIGURE 5 shows a side view of the extruded product.

FIGURE 6 is a section on line 6-6 of FIGURE 5.

Turning now to a description of the drawings by reference characters, there is shown in FIGURE 1 a fuze 6, composed `of a deagrating material coated on a copper wire. Said fuze passes through the central burning port 8 of the propellant grain 10 and is held tightly by a construction in said port at 12. A nozzle 14 is placed around the uze 1 at the rear of the propellant grain 2. This assembly is supported by the free end of the fuze and dipped in hardening plastic 16. Said plastic coats the outside of the grain and nozzle, and follows the extension of the fuze 18 to form a complete structural case 20. The piece may be dipped a number of times to build up the desired wall thickness.

In FIGURE 2, a similar fuze Z2 has been tipped with a metal cone 24 which acts as a stopper to hold the propellant grain 26 and the nozzle 28 in place. The outside of this assembly has been sprayed or dipped with a co-nductive coating such as graphite 30. Upon immersion in plating solution 32 containing metallic ions, the copper center in the fuze is used as an electrical connection to plate a structural metal case around the propellant, tip and nozzle. The fuze 22 need not be employed as the conducting element and other means can be employed to connect the graphite coating to a source of electricity.

The propellant grain 34 and the nozzle 36 shown in FIGURE 2 are rotated in the direction of the arrow by the mandrel 3S which is held and driven by a suitable source of power. A strip of fiber 40 is fed onto the rotating grain and nozzle and is sprayed continuously with a hardening plastic from jet 42. A conical plug 44 of suitable material, either metal or plastic, attached to the end of the grain, completes the aerodynamic shape. Of course, the winding ber 40 may be round instead of flat and more than one pass could be used.

In the cross section of a co-extrusion die 46, FIGURE 4, are shown balanced chambers for plastic supply 48, and for propellant 50 while core 52 forms the central burning port 54 in the Iinished extrusion. The front wall o die 46 is indicated at 68 and includes the aperture through which the extruded product is discharged to atmosphere. The phantom lines extending to the left of FIG. 4 show the extruded concentric walled product and the outer plastic casing, integrated with the iin 58, being ejected from the die. FIGURES 5 .and 6 show the extruded case 56, complete with ns S8 and the central propellant grain 60. The tin section 62 indicated in phantom lines has been cut away, and a nose portion 64 and nozzle element 66 added.

It is also to be observed from a careful examination of the drawing in FIG. 6 that the fore extremity of the propellant grain is appropriately shaped, as shown at 60', to facilitate the assembly of the nose portion 64 therewith. This shaping step may be accomplished in any convenient manner.

Although several embodiments of the invention have been depicted and described, it will be apparent that these embodiments are illustrative in nature and that a number of modifications in the article and its method of manufacture may be effected without departing from the spirit or scope of the invention as delined in the appended claims.

I claim:

1. The method of constructing a miniature solid propellant rocket, said rocket having a central burning port, a propellant grain surrounding and forming said port, a plastic casing enclosing said propellant grain, and a nozzle disposed in the aft end of said casing, comprising introducing an initially-fluid, ultimately-solidifying propellant mixture into a cavity about a mandrel to form an extrudable substantially self-supporting tubular propellant grain; advancing the propellant grain in said cavity to achieve cohesion, extruding into said cavity and in intimate contact with said cohesive tubular propellant grain a settable plastic material whereupon the extruded product is discharged into the atmosphere, cut to length and a nozzle is secured in the aft extremity of the casing adjacent to said propellant material.

2. The method of constructing a miniature solid propellant rocket as claimed in claim 1, wherein a plurality of tins are extruded integral with the casing and severing from said casing a predetermined portion of said fins to provide the rocket.

3. The method of constructing a miniature solid propellant rocket, said rocket having a central burning port, a propellant grain surrounding and forming said port, a plastic casing enclosing said propellant grain, a forward nose portion, a fuse and a nozzle disposed in the aft end of said casing, comprising introducing an initially-Huid, ultimately-solidifying propellant mixture into a cavity about a mandrel to form an extrudable substantially self-supporting tubular propellant grain; advancing the propellant grain in said cavity to achieve cohesion, eX- truding into said cavity and in intimate contact with said cohesive tubular propellant grain a settable plastic material, positioning an elongated fuse in the passage in said tubular propellant grain with the fuse extending the entire length thereof, securing a tapered nose portion to the fore extremity of said casing, and inserting a nozzle element in the casing in contact with the propellant material.

(2i, References Cited by the Examiner UNITED STATES PATENTS 1,036,176 8/1912 Bickel 102-98 X 1,376,376 4/1921 Huntoon 207-10 2,217,451 10/1940 Patnode 18-59 2,501,690 3/1950 Prendergast 264-177 2,626,805 1/1953 Carlton 18-55 2,687,553 8/1954 Colombo 18-13 2,993,236 7/1961 Brimley et al. 18-59 2,995,011 8/1961 Kimmel 60-35.6 2,998,772 9/1961 Land 102-98 3,000,308- 9/1961 Land et al. 149-19 3,010,355 11/1961 Cutforth 102-98 X 3,017,746 1/1962 Kiphart 60-35.6 3,032,970 5/1962 Fox 60-35.6 X 3,051,991 9/1962 Hanzel 264-3 CARL D. QUARFORTH, Primary Examiner.

LEON D. ROSDOL, Examiner. 

1. THE METHOD OF CONSTRUCTING A MINITURE SOLID PROPELLANT ROCKET, SAID ROCKET HAVING A CENTRAL BURNING PORT, A PROPELLANT GRAIN SURROUNDING AND FORMING SAID PORT, A PLASTIC CASING ENCLOSING SAID PROPELLANT GRAIN, AND A NOZZLE DISPOSED IN THE AFT END OF SAID CASING, COMPRISING INTRODUCING AN INITIALLY-FLUID, ULTIMATELY-SOLIDIFYING PROPELLANT MIXTURE INTO A CAVITY ABOUT A MANDREL TO FORM AN EXTRUDABLE SUBSTANTIALLY SELF-SUPPORTING TUBULAR PROPELLANT GRAIN; ADVANCING THE PROPELLANT GRAIN IN SAID CAVITY TO ACHIEVE COHESION, EXTRUDING INTO SAID CAVITY AND IN INTIMATE CONTACT WITH SAID COHESIVE TUBULAR PROPELLANT GRAIN A SETTABLE PLASTIC MATERIAL WHREUPON THE EXTRUDED 